Characterization of peripheral immune cell populations in stable and progressive Alzheimer’s disease

Abstract

AbstractBackgroundAlzheimer’s disease (AD) is the most common type of dementia which results in debilitating memory loss as the disease advances. In addition to the amyloid plaques, tau tangles, and neuronal inflammation characteristic of AD, there is strong evidence of dysregulation in the peripheral immune system, including decreased naïve T cells and increased memory T cells among older adults with AD. However, the involvement of the peripheral immune system in the neurodegenerative cascade leading to AD is poorly understood. Furthermore, among older adults with AD, some may experience rapid cognitive decline while others may maintain a stable cognitive status for years. It is currently unknown whether dysfunction in the peripheral immune system is associated with neuronal inflammation and cognitive decline.MethodIn our ongoing work, we are longitudinally characterizing resting peripheral immune system cells by flow cytometry and here present data from a subset of those with AD (n = 19) or no dementia (ND, n = 93) whom we have followed for >1 year.ResultWe have identified an increase in B cells (percent all lymphocytes, AD 6.4 (SD 8.6) vs ND 4.0 (SD 2.4) p = 0.031) and CD4+/CD62L+ naïve T cells (percent CD4+ lymphocytes, AD 33.4 (SD 18.4) vs ND 25.4 (SD 14.1) p = 0.034) among AD patients. Among the population of AD patients experiencing cognitive decline (n = 4) determined by increasing ADAS‐Cog score >6 points over one year compared to stable scores (n = 11), we have discovered a decrease in CD4+/CD62L+ naïve T cells (percent CD4+ lymphocytes, stable 33.9 (SD 14.5) vs declining 20.5 (SD 16.1) p = 0.049), increase in effector memory CD4+ T cells (percent CD4+ lymphocytes, stable 28.2 (SD 4.8) vs declining 47.0 (SD 6.5) p<0.001), and increase in B cells (percent all lymphocytes, stable 2.6 (SD 1.5) vs declining 5.3 (SD 1.8) p = 0.010), when compared to older adults with AD and stable cognitive status.ConclusionThis longitudinal clinical study identifies changes in resting peripheral B and T cell populations in AD patients and among AD patients with cognitive decline.